W. Bateson 97 



endogenous but may be originated by a periclinal division in the cortical 

 layer. 



In such an example as the crumpled zonal here described, or indeed 

 in any periclinal chimaera with patches of its core coming out on the 

 surface of leaves, the jjrocess by which this change is brought about is 

 very difficult to imagine and I do not know how it may be represented. 

 The growing point must contain both elements, but the emergence of that 

 which is normally enclosed seems at present to be purely fortuitous. 



As regards reversals of the layers, such as I described in Jour. Gen. 

 VIII. 1919, p. 94, it is worth observing that though we have now fairly 

 numerous cases of white-over-green turning to green-ovcr-white, a change 

 which in some plants happens frequently, we have not hitherto seen a 

 single instance of the contrary. Of Euonymus, some zonals, an ivy-leaved 

 Pelargonium, and Arahis we have several large and well-grown plants 

 of the green-over-white kinds, but though occasionally the white has 

 come to the surface in a small area, no reversal has been found on such 

 plants. Possibly we may regard white-over-green as an arrangement 

 mechanically less stable than green-over-white. 



Several attempts have been made to breed the root-cuttings with 

 their parent plants, an experiment offering attractive possibilities, but 

 we have hitherto been unsuccessful. 



EXPLANATION OF PLATES. 



PLATE XIII. 



Fig. 1. Pelargonium Escot. 



Fig. 2. Boot Cutting of Escot. 



Fig. 3. Pelargonium Mrs Gordon. 



Fig. 4. Boot Cutting of Mrs Gordon. 



Fig. 5. Pelargonium Pearl. 



Fig. 6. Root Cutting of Pearl. 



Fig. 7. Flower with red blotch, a form occasionally seen on Pearl. 

 This plate is from drawings by Mr C. H. Osterstock. In the photograph the colours 

 of Escot and the two forms of Mrs Gordon are approximately correct. In Escofs root- 

 cutting the red should be distinctly brighter, without any bluish tinge, and the same applies 

 to the red colour in figures 6 and 7. 



PLATE XIV. 



Fig. 1. Zonal Pelargonium Golden Flame. On the right is seen the foliage of the type, 

 which is buckled and shiny. On the left the sport, with leaves flat and dull. The two 

 right-hand inflorescences are laciniated. The two left-hand inflorescences bear mixed 

 flowers, some entire, some laciniated. The fruits formed in two entire flowers are 

 ■visible. These mixed inflorescences belonged to the area of transition. 



Fig. 2. Spiraea ulmaria: leaf of variegated form. 



Fig. 3. ditto leaf of normal green form. 



